Hypothesis
by Silent Epiphany
Summary: A night of friendly drinks turns into one of debauchery in a single slip of the tongue. YAOI, SteinxSpirit. Explicit LEMON! Don't like, don't read!


_**Hypothesis**_

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**Disclaimer:** _Soul Eater _and everything related to it are property of Atsushi Okubo and other creative individuals who aren't me.**  
Warning: ****_**Explicit YAOI lemon** **__Those offended by GRAPHIC male/male sex should TURN BACK NOW._**  
Pairing: **SteinxSpirit**  
Author's Notes:  
**Another lemon for my OTP of this fandom. ^_- Hawt diggity dayum. This is intended to be set somewhere before the series, as Stein is fresh out of med school. Make your own ages and timeline (as if it _really_ matters).

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"Is there a doctor in the house?" Spirit cawed drunkenly, rising from his seat to catch stares from all others in the tiny bar. "Oh wait—_now_ there is!"

Across the round booth from him was his former meister and recent recipient of his medical license, Franken Stein. Or, should he say, _Doctor_ Stein. Spirit couldn't help but grin at the way the title seemed to suit him. It fit nearly as well as the white labcoat he'd taken to wearing. Of course, that much could've been because of the fact that all the seams on it had been replaced with sutures. The doctor's personal handiwork, without a doubt; they matched the scar cutting across his cheek too well for it to not be.

Meanwhile, unaffected by his friend's chipper mood, Stein dug his elbow into the top of the small table between them and propped his chin on an upturned palm, letting out an exasperated sigh. This whole thing had been a really bad idea. Had he known Spirit was going to make such a big deal about his finishing his residency and obtaining his medical license, he would've never agreed to this horrid excuse for a party. It wasn't really even a party in the first place; it seemed more like a reason for his former weapon partner to get completely snockered, which hadn't taken him long.

Once that had happened, the terrible doctor puns began, and hadn't ceased since. Stein had heard them all ad nauseam. One more and he was going to hit the chatty redhead with his soul wavelength. Not _hard_, mind you—just enough to knock him out for a while, that was all. He'd do it discreetly so no one would notice, and then escape from this trap he'd unwittingly been locked into.

"I always knew you had it in ya!" Spirit continued to verbally applaud. "How's it feel to finally _get paid_ for cutting people open, huh?"

The comment made several patrons around the cramped establishment cast unsettled looks in the young doctor's direction. One by one Stein turned them all away with a moment's passing glance from his cold jade eyes. As a matter of fact, the only person that seemed to be ineffective on was his former weapon, who continued prattling on raucously, earning a warning from the barkeep.

Unfortunately Spirit, in his fuzzy state of mind, didn't take kindly to such requests, and wasn't about to be quiet about such.

"Who do you think you are? You can't talk to me like that! I'm a Deathscythe, dammit!" He countered, slurred words filled with drunken bravado, and thumbed his chest…and nearly his eye. Others in the area eyed him critically.

It wasn't long after _that_ outburst that the bartender took the liberty of cutting the mouthy redhead off, and he and his companion found themselves out on the moonlit street. It was just as well, Stein mused, as alcohol seemed to have brought out an even more obnoxious side of his former partner, if that was even possible. As a result, he wasn't completely averse to calling it an evening. More accurately, at the moment, he was in favor of it. His companion, however, was of a different opinion.

"No, no—you can't take me home like this—Kami'll _kill_ me if I come home _this _smashed!" The redhead dismissed with a rather fanatical yet slow-motion wave of his hand.

"Well then?" The new doctor gestured in the general direction of his personal home.

"No way!" Spirit refused, physically balking at the suggestion. It seemed that of the two given options, he'd prefer a brutal and certain death at the hands of his wife over the multitude of things that could potentially transpire at the laboratory. "I don't care if you _are_ a doctor now—there's no way I'm gonna let you split me open again!"

"On the contrary," was Stein's simple response. Startlingly enough, he hadn't given much thought to the idea of cutting into his greatest experiment again. Of course, with the idea freshly replanted in his mind, he couldn't deny that it sounded good. It definitely had the potential to turn an otherwise lackluster evening into something entertaining. Furthermore, with Spirit nearly swaying where he stood with intoxication, getting to dissect his favorite specimen once more was a real possibility.

After a moment of questioning silence, Stein was headed back in the direction of his residence, stumbling drunk weapon in tow.

"Hey, y'wanna know somethin' really funny?" Spirit offered, swinging an arm over the scientist's shoulders for added support and balance as they walked.

The scientist blinked at the unexpected contact, but remained very obviously uninterested in whatever the weapon had to say. His silence, however, was taken as an open invitation to continue.

"When we were in high school—at Shiba…Shinu…"

"…Shibusen."

"Yeah, that place," he accepted with a drunken point of his index finger, "…back then, I had the _biggest_ crush on you." The last part came in a whisper with half-lidded eyes and an attempt at a somewhat sultry look. He didn't seem to notice the awkward hush that ensued, or the abrupt pause in his green-eyed companion's steps.

"We _lived together_ during that time," Stein clarified after a moment, "you were dating your wife."

"I know," Spirit half-giggled, "kinda made things _complicated_, if ya know what I mean…" There was a wink on the end of that statement. Stein could very well guess its meaning. "I'm s'prised you never caught on…you'd think a smart cookie like you'd figure it out, but nope! You were totally clueless."

The scientist suppressed a wicked smirk. Although his former partner's candor was completely unwarranted, it had led him to a new hypothesis he'd like to test.

For the first time that evening, things had finally gotten interesting.

…

Using what fuzzy logic he'd had available to him, Spirit had previously deduced that the secret to leaving Stein's lab with all his existing organs and tissues intact was staying awake. All he needed to do was make sure he didn't pass out, which seemed simple enough. Surely if he could manage that there'd be nothing to worry about.

Or so he thought.

No sooner than the door to Stein's laboratory closed, Spirit found himself at the mercy of the new doctor. In a blink, he'd trapped both of the weapon's wrists above his head, pressing them tightly against the cold wall with one hand.

The haziness of Spirit's intoxication evaporated, burned from his veins with one glare from those haunting jade eyes, which almost seemed to glow with artifice.

"Dammit Stein, I'm not your toy," the redhead growled, though failing to sound even remotely menacing. "And I'm done being your science experiment! Now let me _go!"_

He wriggled and squirmed in an attempt to fight the contact, but made little headway in getting his captor away from him. Instead, Stein only moved in closer, seizing him by the jaw with his free hand. The action seemed to freeze the weapon instantaneously. At once, his struggling ceased.

The scientist forcibly pushed his companion's face away, making delectably sensitive flesh readily accessible to him as he lurched in further.

"This is what you wanted it, isn't it?" he breathed into an ear. Spirit could feel his former meister's lips mere millimeters from the flesh of his earlobe, a sensation that made him shudder. He swallowed hard, his eyes darting about to avoid contact with any part of the man, all the while the color on his cheeks told the answer.

Even through the distance between them he could feel Stein's smirk. Beneath his tie, dress shirt and blazer, the hair on his arms stood at attention.

...Along with something else much further south.

How again had he gotten himself into such a mess? He'd only been seeking to give his old friend—and new doctor—a bit of congratulations in the form of a night out for drinks. But, as he had a penchant for doing, he'd consumed too much and said too much. Usually, it was a bad thing. This time, however, he found himself being swept away into a whirlwind of impossibilities come true, which seemed to be far worse. He was a married man—a _father_—and Stein was nothing more than a predator without a conscience. But those words mattered little to the rest of his body it seemed, as he felt his arousal pulse greedily against the fly of his slacks, reminding him that he did indeed want it. He wanted the breath on his skin, the hands pressing against him, and to see the silver-haired scientist's normally distant and apathetic expression impassioned with lust and desire. To see a crazed look on his face that meant he was going to be hurt only in all the _right_ ways…

He could feel a warm wetness on his neck as Stein swept his tongue over the tender skin. Again Spirit wriggled and writhed between the wall and the one pinning him there, a low moan trapped deep in his throat. The frame of his former meister drifted closer, inundating him with the raw pleasure from sweet, delicious friction, and Spirit could feel his silvery-haired companion's arousal brush against his own. He found it strangely reassuring, as if it told him he wasn't merely caught up in one of Stein's cruel games. Or that if he was, at least there were two players.

"So, I'm not the _only _one who's been keeping a secret…" the redhead remarked and allowed himself a grin, even against his own plight.

"'I'm surprised you never caught on,'" Stein repeated mockingly, feeding the weapon's own words back to him.

Spirit's immediate plan had been to fumble for a snarky remark, but his mind was instead far more preoccupied with something else. Particularly the presence of the hand which had slipped from his jaw and was undoing his pants, seeking out his length and finding it with little trouble.

Stein's fingers curled around him gently and gave a painfully torpid stroke of the silken flesh that had the other arching off the wall, silently pleading for more.

"Now tell me, senpai…what _else_ did you want?" the silvery-haired man queried in a husky, seductive tone that Spirit didn't know he was capable of. He suppressed a shiver, but felt his cock twitch all the same.

He answered meekly, "…You."

Another lingering, leisurely caress to his hardness.

"You're going to have to do better than that."

His mind had a wealth of responses; a slew of fantasies of what he'd do in this exact situation. Things that had been a secret guilty pleasure on many a lonely night, even in the not-too-distant past. Ideas that had been fodder for plenty of previous orgasms, even dating back to the year when he'd first developed an inexplicable attraction to his silvery-haired young meister.

And yet, in light of being actually confronted with the opportunity to realize those fantasies, the only answers he seemed to be able to form were unintelligible broken sentences mixed with gasps and whimpers.

Another painstakingly slow stroke of his cock and Spirit bit his lower lip roughly. How could Stein expect him to form rational thought when he was doing such things? Every inch and every second of contact only further obscured his ability to reason. How could he, when he had been reduced to nothing more than a mass of nerves? Every sense he had was acutely aware of—and centered upon—the scientist's presence and actions. With every surgically precise graze of his skin his body uncontrollably reacted, shivering, bucking, and trembling underneath it. His hips desperately moved against the hand caressing him, begging for it to move again. Faster, harder—hell, _any_ sort of friction would suffice, as he wasn't feeling particularly picky at the moment—but still Stein wouldn't give in to the request. Instead, he adamantly disallowed Spirit to have any physical control over their encounter until he got his answer.

The human weapon released the bite on his reddened lip long enough to breathe three discernable words. They were specifically what Stein had wanted to hear, spoken in precisely the right way to make his arousal ache, throbbing hungrily against the constraints of his clothing.

"…Just fuck me."

Before Spirit's mouth could busy itself with anything else the scientist captured it, his tongue plunging greedily into its warm recesses. The redhead willingly surrendered, as fighting it—if he'd even wanted to—was a distant afterthought. In an instant, his senses were flooded with the distinct flavor of his companion. He tasted just like his former weapon had always imagined he would: of cigarettes, and black coffee, and desire, and oh God Spirit just didn't care anymore—the hedonism present in his very nature had finally won over. So long as he eventually found release from the ubiquitous and all-consuming passion swirling in his body, he would endure whatever was necessary to get there. He would give himself over; he'd let himself be controlled. Anything. Anything for pleasure. Anything for _release_. He didn't want it nearly as much as he _needed _it. Desperately, he moaned into Stein's invasive kiss, and the scientist could feel the pressure against the palm pinning his companion recede.

At last, he had Spirit exactly where he wanted him.

Again far quicker than he'd expected, he found himself flipped around, facing the same place he'd once leaned against. Slender fingers curled in his crimson hair, clawing as if of their own accord while the same hand simultaneously pushed, forcing his cheek against the wall.

In one swift movement his lower garments were pooled around his feet, binding him where he stood. The hand once around his member returned, fingers sliding up to the head to steal some of the liquid anticipation he was drenched with before rescinding. Infuriatingly indolent, they ghosted over the nearby flesh of his hip and around the smooth curve to his backside. A single digit trailed down the cleft between his cheeks, and then he could feel the familiar warm dampness upon a single digit as it circled his most private part, questioning but not hesitant. Spirit barely had time to flinch before it dipped in, and was joined not long after by a second. On the heels of that was what he was certain was a third, opening him even further, leaving him mewling desperately, bereft of all formal, intelligible language. Involuntarily, his body jerked, entirely on edge. Each beat of his heart slammed against his throat, his pulse felt racing throughout his entire form.

"This will be easier if you relax," came Stein's low voice, tone someplace between calm and cold; Spirit couldn't discern exactly where.

Relax? He made it sound so simple, but at that moment, it was the furthest thing from possible. There was _no way_ he could relax. Not while he was in Stein's laboratory, not while his pants were around his ankles, and most _certainly_ not while he had three of said man's fingers in his ass.

But, surely if he closed his eyes he could be somewhere else, touched by anybody other than his former meister.

At the mere thought he swallowed hard and felt his stomach knot, sick with the knowledge that he didn't _want_ to be anywhere else. He wanted it to be Stein, plunging his digits in deeper, violating him in a way that somehow inexplicably aroused him.

It was dirty. It was wrong. And he loved every second of it.

It made him crave the hardness that had once pressed against him, and long to feel it grow and throb inside him.

The scientist's fingers pushed in further. It was a rather uncomfortable sensation initially, until the moment they struck something glorious within his body, and pleasure exploded within him like the jolt from an electric current. At once, the tension in his muscles vanished along with his breath, and his heart jumped in his chest. From beyond Spirit's line of sight, the doctor grinned wolfishly.

Only a moment lapsed before he replaced his digits with his length, stealing the weapon's words, silencing his voice, breath inclusive. He lurched up onto the wall, desperately clawing at it with whitened fingertips, scratching to have something—_anything_—to hang onto. He'd never had the sensation of being consumed, taken, filled to the brim; nonetheless by Stein, of all people. Sure, he'd fantasized. Hoped and dreamed. But his meister was always so cold and distant, uninterested in anything beyond scientific endeavor. A stark contrast to their present situation in every way, from the hand curled around his hip, pulling his body into their union, and the other that bypassed that and proceeded forward, gripping his cock. Every caress of his member by the silvery-haired man's palm made him pant…every rock of his hips made his body arch into it of its own volition.

He twitched and trembled, breaths shaky and rapid. He wouldn't last much longer. He _couldn't, _with Stein's expertly executed strokes combined with his hypnotizing touch. He was going to spill over. He was going to-…

Suddenly, everything came to a screeching halt. Stein's actions ceased, and everything in Spirit's body screamed. Everything except for his voice. He was so hard it hurt, and so near the precipice of ecstasy that it was maddening. Stein had to know, and yet he remained motionless, waiting. Immediately, and still with no words within reach, his mate began to whimper and babble his discontent.

"Don't stop!" he fumbled out at last, trembling with anticipation unlike anything he'd felt before. "Don't stop, Stein…please!" Spirit had never begged in his life, let alone so earnestly; but he'd also never needed anything quite as bad. "Please!" he cried out, having no other words to say. Sapphire eyes wrenched shut, voice breathy and desperate. "Please—_ah, God_—_please!"_

At last, Stein knew he had Spirit's complete compliance. His surrender. His absolute submission. It delighted him in ways nothing else on Earth ever had or ever would.

With such sincere requests, he couldn't help but oblige.

He gave his precious former weapon what he asked for, driving into him with ferocity that had the other actively bracing himself against the wall. Spirit took him in as much as his body would allow, eagerly matching his lover's every thrust. At last the unmistakable sound of flesh against flesh could be heard, and the redhead gasped for breath like someone who had been drowning as they reached the surface.

Unable to fight his response, Stein shuddered hard. Senpai certainly knew how to make some amazing sounds. Every delicious gasp—every whimper or cry, subtle or loud—sent sparks racing down his spine, settling in his groin. Each drove him, filling him with urgency, desire, and unadulterated passion that fueled the fire burning hot under his skin. His pace quickened, body surging against his mate's, feeding back into the cycle he wished to be endless.

Deep within him Spirit could feel his partner's pulse escalating, rising, and reverberating through him louder than the thumping of his own erratic heartbeat. Louder than the low, feral grunts and groans of his partner, and the near-screams repeatedly tearing themselves from his own throat. His body seared and shook, quivered and ached, as if mere moments from total breakdown. And in the most glorious of ways it would break down, much the same as some part of him already had.

And he would never forget who had been behind it all.

At last, Stein struck the same glorious spot within him that he'd touched earlier, and sealed his fate. With all the grace and force of a tidal wave, pleasure crashed over him, permeating every inch of his form, sweeping him away into ecstasy.

The last thing Spirit recalled was succumbing at last, his body spilling over and slipping, tumbling, sinking down into the blissful infinite blackness of undertow.

…

An unknown amount of time passed. Mere minutes or perhaps even hours, Spirit wasn't certain. Wherever he was and however long he'd been there he was certainly comfortable, his body entirely lax, muscles still humming with the aftershocks of climax. He was warm, and felt somehow surprisingly at peace. It was as though he was within a niche in the world that had been perfectly carved out just for him. He belonged there. It made him feel whole, complete.

Blearily, his sapphire eyes fluttered to life to see that that sublime, euphoric place he had been…it was within Stein's grasp. On the floor against the same wall of the patchwork laboratory, they were a tangled mess of one another. Somehow Spirit had nearly worked his way into his former meister's lap, the silvery-haired man's arms lazily slung around him. The weapon lifted his head and a depthless yellow-green gaze stared back at him, the grin within them just as smug as the one on their owner's lips. It was the look of someone who had just unraveled a great mystery or stumbled upon some deep-hidden truth.

Actually, Spirit mused, that was quite the accurate description. Like it or not, it summed everything up rather well.

"Don't get any ideas," he mumbled, tone half-pouting.

Stein's head tilted just slightly. Ideas? Why would he need those? He'd confirmed his hypothesis; there was nothing left up to question.

"I mean it, Stein. Don't read into this. I'm still a married man with a family, and—"

Without warning, the weapon's words were abruptly muted by the presence of his companion's lips against his own. Their meeting was not impulsive or desperate as before, but instead gentle, soft, tender, and lasting. A part of Spirit delighted in the way the Stein's lower lip lingered against his own for moments after their lock broke. Never before had he been kissed that way; not even when he and Kami had stood at the altar. Inside his chest something did a strange little flip and he could feel his cheeks darken, only a few shades off from the vibrant crimson of his hair.

In addition to everything else, he even blushed rather spectacularly, Stein decided. Unconsciously, a pale hand moved upward and brushed across one of those reddened cheeks, darkening all in its wake as though it had been a brushstroke of scarlet.

Perhaps it was the way the rosy color contrasted the pale blue of his eyes, making them appear brighter than they already were. Or perhaps it was that he knew that blush was all for him. _Because _of him.

Only for him.

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**~OWARI~**

**ANs: **This fic brought to you by the many musical musings of Garbage, including but not limited to "You Look So Fine", "Push It", "Wicked Ways", "Bad Boyfriend", and "Sleep Together".

Random: My (male) professor literally used the phrase "Hot and heavy, fast and dirty." I hope I accomplished at least two of those in this fic.


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